How did early lunar and Mars spacecraft capture and transmit photos before modern digital cameras?
Asked 10/11/2016
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I’m curious how very early space missions handled imaging before modern digital cameras were common. For example, Luna 3’s 1959 photos of the Moon’s far side and the Viking landers’ 1976 Mars images.
Did these spacecraft use photographic film, video tubes, or some early digital sensor? If film was used, was it actually developed onboard? And once the image was captured, how was it sent back to Earth—purely as an analog radio signal, or as some kind of scanned image data comparable to a bitmap/raw image?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
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Luna 3 did something as complicated as you thought: It took photos on a film, processed it in a kind of onboard minilab, and then scanned and radioed it back home in analog way not unlike an old fax.
Funniest part was that Soviets didn't have the technology of radiation-hardened film, but Americans did. They used it against Soviets in high-altitude spy balloons. This program was quite a failure for Americans, but Soviets retrieved some of those balloons before they spent their precious cargo and repurposed the film for a space mission. Manufactured in the USA, sent to the Moon by Soviet Russia! You can read more about Luna 3 here
If you ask about similarities to raw "format", analog picture transmission is more like uncompressed bitmap than raw dump from a typical modern sensor. Raw data is not a format, every sensor makes it's own and there are no metadata like end-of-line markers or info about what sensel represents which color. Analog transmission (as in fax or TV) usually is way more structured, eg time to return the scanning beam to the beginning of the next line makes a natural end-of-line marker, or a special tone is used to denote that, which among others allows at least partial recovery of the image if there are some hiccups.
Originally by user37063. Source · Licensed CC BY-SA 4.0
user37063
9y ago
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Early spacecraft used several different imaging methods depending on the era and mission.
Luna 3 (1959) used photographic film. The film was exposed onboard, chemically developed inside the spacecraft, then scanned line-by-line and transmitted to Earth by radio in a way broadly similar to fax image transmission.
By the Viking landers (1976), the system was different. Viking did not use roll film like a normal camera. Its lander cameras were facsimile-style scanners with a stationary photosensor array and mechanical scanning in azimuth and elevation to build up an image over time.
Another important pre-modern-digital technology was the video camera tube, such as a vidicon. These worked by forming an image on a photosensitive surface and electronically scanning it to produce a signal.
So the answer is: before modern CCD/CMOS cameras, spacecraft often used film with onboard development and scanning, or electronic scanning systems like vidicons/facsimile cameras. The transmission back to Earth was typically a radio signal carrying the image as sequential scan data, more like an uncompressed bitmap or faxed image than a modern camera raw file.
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